Ever since Viagra met blockbuster success in 1998, the drug industry has sought a similar pill for women.Now, a German drug giant says it has stumbled upon such a pill and is trying to persuade the Food and Drug Administration that its drug can help restore a depressed female sex drive. The effort has set off a debate over what constitutes a normal range of sexual desire among women, with critics saying the company is trying to turn a low libido into a medical pathology.On Wednesday, an F.D.A. staff report recommended against approving the drug, saying the maker, Boehringer Ingelheim, had not made its case and that the benefits of the daily pill did not outweigh its side effects, which included dizziness, nausea and fatigue.That staff report came ahead of a meeting Friday by an F.D.A. advisory panel of experts who are to vote on whether to recommend that the agency approve the pill, which would be the first drug aimed specifically at a low sex drive in premenopausal women.F.D.A. staff reports carry weight but do not always sway how advisory panels vote, and advisory votes do not always predict what the F.D.A. might finally decide.Some analysts forecast that if the drug does reach the market, it could have annual sales in this country of $2 billion — or about equal to the current combined annual American sales of the men’s drugs Viagra, Levitra and Cialis.In the last month, Boehringer has been trying to lay the consumer groundwork with a promotional campaign about women’s low libido, including a Web site, a Twitter feed, a Discovery Channel documentary and a publicity tour by Lisa Rinna, a soap opera star and former Playboy model, who describes herself as someone who has suffered from a disorder that Boehringer refers to as a form of “female sexual dysfunction.”There is no dispute that some women have a depressed level of sexual desire that causes them anguish. Boehringer cites a condition — hypoactive sexual desire disorder — that is included in the Diagnostic and Statistical Manual of Mental Disorders, a reference book for psychiatrists and insurers.But many experts say that unlike sexual dysfunction in men — which has an obvious physical component — sexual problems in women are much harder to diagnose. And among doctors and researchers, there is serious medical debate over whether female sexual problems are treatable with drugs. Some doctors advocate psychotherapy or counseling, while others have prescribed hormonal drugs approved for other uses.There is also debate over how widespread hypoactive sexual desire disorder actually is among women. The medical literature, including articles in the prestigious New England Journal of Medicine, indicate numbers above 10 percent, but such studies have been financed by drug companies.Critics say Boehringer’s market campaign exaggerates the prevalence of the condition and could create anxiety among women, making them think they have a condition that requires medical treatment.“This is really a classic case of disease branding,” said Dr. Adriane Fugh-Berman, an associate professor at Georgetown University’s medical school who researches drug marketing and has studied the campaign. “The messages are aimed at medicalizing normal conditions, and also preying on the insecurity of both the clinician and the patient.”Boehringer developed the drug, flibanserin, as an antidepressant, but it failed to lift depression. The company says it learned serendipitously that the pill, taken daily for weeks, could restore female libido.Dr. Peter J. Piliero, Boehringer’s director of medical affairs in the United States, says the lack of libido to the point of distress is a serious problem for some women.“This is a real disease,” Dr. Piliero said in an interview. “There’s an unmet medical need among premenopausal women to have a treatment.”Boehringer says the drug reduces the brain chemical serotonin, which can blunt sexual desire, and increases dopamine and norepinephrine, which improve desire, the company said. By acting on a woman’s brain, it takes a different approach from hormonal drugs or the action of Viagra for men, which increases blood flow.Boehringer’s application for F.D.A. approval said that its two key 24-month studies, of 1,323 premenopausal women who said they suffered distress over lack of libido, had found small but statistically significant improvements. The women lived in the United States or Canada, were mostly married, well-educated and found to have the sexual desire disorder but were otherwise healthy.In results reported last fall at a medical conference in Europe, the drug was found to increase self-reported “sexually satisfying events” to 4.5 a month on average. The reported events, which did not have to include orgasm, compared with 3.7 a month by women taking a placebo and 2.7 by those who did not take any pills.The F.D.A. staff report on Wednesday, though, said that Boehringer’s data had not sufficiently demonstrated a second criteria the agency had set for approving such a drug — specifically, that women also report an increased level of sexual desire. The F.D.A. required daily self-reporting by the women in the studies; Boehringer said it had provided monthly reports.Lara Crissey, a spokeswoman for Boehringer, declined to comment on the F.D.A. staff report.Other drug companies that have sought a drug to elevate women’s sexual desire have included Pfizer, which spent several years trying to show that its drug Viagra could work for women as well as men. When Pfizer ended that research in 2004, it said in a news release that female sexual disorders resulted “from a broad range of medical and psychological conditions.”Procter & Gamble sought F.D.A. approval for a skin patch to raise the testosterone levels of women who had had their uterus and ovaries removed, but it was rejected in 2004 because of possible links to breast cancer and cardiovascular disease. In 2006, though, European regulators, saying the testosterone patch appeared safe at low doses, approved that drug to treat depressed sexual desire in women whose uterus and ovaries had been surgically removed.BioSante Pharmaceuticals, a company in Illinois, is in late-stage testing of another testosterone patch product which it hopes to submit to the F.D.A. next year. And Vivus, a drug development company, is testing a testosterone-based daily abdominal spray for women which it says has proved effective in early trials. And other research is focusing on the antidepressant buproprion, better known as Wellbutrin or Zyban.Dr. Steven E. Nissen, a Cleveland Clinic cardiologist and a member of the 2004 F.D.A. panel that unanimously rejected the testosterone patch, said that the depressed desire disorder was a real medical condition, especially for middle-age or older women, with both physiological and psychological causes.“I got a lot of hate mail after that vote,” Dr. Nissen recalled. “People wrote me and said, ‘You men have your Viagra, why are you denying us this?’ I said hey, I’m just trying to do the right thing. It needs to be scientifically sound.”Dr. Nissen said he had not studied the Boehringer drug.Leonore Tiefer, a psychologist and professor at New York University who has researched the topic of female sexual desire for more than a decade and plans to testify to the F.D.A. panel on Friday, said Boehringer had gone too far with its publicity effort.“Women’s sex lives are often a struggle, a disappointment, an archipelago of regret,” she said. “Is there a small group of women who could benefit from medical intervention — probably.”But she said that if the drug were approved, she worried that “the much larger group of women without any medical reason for their sexual distress will inevitably be misinformed and misled into thinking that there is a pill that can get them the sex life they read about, the one they think everyone else is having.”Boehringer has also sponsored medical education classes for doctors and nurses about hypoactive sexual desire disorder.In one course, released online in May, a quiz asked doctors to diagnose the condition of a 42-year-old working mother who takes care of three children and her own sick mother, and who had no desire for sex. (Her husband is mentioned only in passing.)The correct answer? Schedule a follow-up visit to evaluate whether she has diagnosable hypoactive sexual desire disorder.